While raised de novo lipogenesis might not be the only mechanism for hypertriglyceridemia in GSD Ia patients,17 the higher abundance of ACACA may lead to an increased demand for biotin and consecutively increased biotinidase levels, which we observed in the GSD Ia liver on transcript level as well as on enzyme activity measurements in GSD Ia patient sera. Here, BTD is linked to hypertriglyceridemia.